Simplify the following expression: ${-n-3(-5n+7)}$
Explanation: Distribute the ${-3}$ into the parentheses: $ -n {-3(}\gray{-5n+7}{)} $ $ -n + {15n-21} $ Combine the $n$ terms: $ {-n + 15n} - 21$ $ {14n} - 21$ The simplified expression is $14n-21$